Generating Transition Dipole, Angular Momentum, and Spin Matrices for Spin-Orbit Coupling in MOLPRO

[Gaurab Ganguly]

Dear MOLPRO Community,

I hope this message finds you all well. I am currently trying to generate dipole moment (Mux, Muy, Muz), angular momentum (Lx, Ly, Lz), and spin (Sx, Sy, Sz) matrix elements between spin-orbit (SO) electronic states and print them to files using MOLPRO.

For a test case, I chose a simple molecule, CH2 carbene (C2v geometry), which does not have significant SO coupling but can serve the purpose of generating those matrix element files. In my specific test case, I'm performing SO coupling calculations between one singlet and one triplet state for CH2 carbene.

In OpenMOLCAS, I was able to achieve this by utilizing the RASSI module, which allowed me to generate property matrices with easily parsable matrix output. These matrices are stored in files named "dipole-[1,2,3].txt," "angmom-[1,2,3].txt," and "spin-[1,2,3].txt." They contain the complex values (REAL and IMAG parts) for dipole moment, angular momentum, and spin matrices between all SO states. Note, index 1, 2, 3 represent Cartesian laboratory coordinate axes x, y, z.

However, I have encountered difficulties in generating/printing the same files with MOLPRO's MRCI program. While I understand that transition dipole moments between electronic states are printed in MCSCF and MRCI calculations, these typically focus on transitions with respect to the lowest energy ground state. My goal is to print the transition matrix elements between all SO states involved for electric dipole moments, angular momentum, and spin matrices.

For your perusal, I am also appending the MOLPRO input file that I am using. It's worth noting that the input ran without any errors. 

I kindly request your expertise and guidance on how to modify my MOLPRO input file to generate these matrices with easily parsable matrix output, similar to what I achieved with OpenMOLCAS using the RASSI module.

Any assistance or insights you can provide will be greatly appreciated. Thank you in advance for your support.

Best regards,
Gaurab

=================================================================

MY MOLPRO INPUT:

=================================================================
***,ch2
memory,5000,M

file,2,ch2.wfu,new

set,DKHO=2     ! second-order Douglas-Kroll-Hess Hamiltonian
set,DKHP=1     ! Optimum parametrization (OPT, default)

gprint,basis,orbital,civector;
gthresh, energy  = 1d-9
gthresh, gradient= 1d-6
gthresh, grid    = 1d-9
gthresh, orbital = 1d-8
gthresh, civec   = 1d-8

symmetry, X Y   ! C2v point group
geomtyp = xyz
angstrom

! triplet optimized geometry

geometry = {
3

C                  0.00000000    0.00000000    0.10286900
H                  0.00000000    0.99608700   -0.30860700
H                  0.00000000   -0.99608700   -0.30860700
}

basis = {C = cc-pVTZ-DK;
         H = cc-pVTZ-DK;}

{rks,b3lyp;
occ,      3, 0, 1, 0;
wf, nelec = 8, sym = 1, spin = 0, charge = 0;
orbital, 2100.2;}
put,molden,ch2.rks.molden;

{multi; !config,csf;
start, 2100.2;
frozen,   0, 0, 0, 0;
closed,   1, 0, 0, 0;
occ,      3, 1, 1, 0;
wf, nelec = 8, sym = 2, spin = 2, charge = 0; state, 1;
wf, nelec = 8, sym = 1, spin = 0, charge = 0; state, 1;
natorb,2140.2;
natorb,2141.2, state = 1.2;
natorb,2142.2, state = 1.1;}
put,molden,ch2.casscf.3b1.molden; orbital,2141.2;
put,molden,ch2.casscf.1a1.molden; orbital,2142.2;

{mrci; noexc; orbital,2140.2;
core,     1, 0, 0, 0;
closed,   1, 0, 0, 0;
occ,      3, 1, 1, 0;
wf, nelec = 8, sym = 2, spin = 2, charge = 0; state, 1;
save,6030.2;}

{mrci; noexc; orbital,2140.2;
core,     1, 0, 0, 0;
closed,   1, 0, 0, 0;
occ,      3, 1, 1, 0;
wf, nelec = 8, sym = 1, spin = 0, charge = 0; state, 1;
save,6040.2;}

{MRCI;HLSMAT,LS,TRANLS,\
   6030.2,\              
   6040.2,             
   print,\
   HLS = 2,\             
   VLS = 1;              
   option,\
   MATEL=1}